Polishing metal and heat treating

I would like to make a hand vise, 2 x 3 inches for filing small parts . Using 1018 steel. Don't know how to mirror polish it and keep tolerances (hoping for .0005 surface) . After doing it needs to be hardened so the file skates across it. If I succeed I would like to make some sine bar standards. Same polish and treatment except finishing to an exact size. Eventually ending up in the .0002-3 range. Doing this to learn how. Any recommendations as to how to proceed or articles/books? Cutting, turning and measuring to size is not a problem, but I have never done a real mirror type finish or heat treating. Thanks Charles

To hold those sort of tolerances I would think the hardening will need to be done first and then a grinding, lapping process to get the final dimension and finish.The work can grow during hardening and distort hence the need to get the final dimension and finish after hardening.

Mike

Edited By Michael Poole on 08/03/2016 01:40:17

Lets start with the hand vise. 2 pieces of 1" x 1-1/2" x 3" long. A couple of alignment dowels and some threaded holes to tighten. Some notches perpendicular to the face for round objects. Put together, tighten, mill flat and indicate to check. I can do that. Where do I go from here? I have only a bench grinder. I will have to make or buy something to grind/polish or lap and keep the dimensions and tolerances. Can I do it on the mill itself? I do have a Paragon Kiln for melting, slumping and annealing glass. It is supposed to get hot enough for heat treatment. If not I have a torch. Ideas wanted. Thanks Charles

.

Surly only the vice jaws would need to be hardened.?

After making them you could send those to away to be hardened and ground to size and finish.

Nick

Nick these small hand vices usually don't have separate jaws, something like this

I really question if 0.0002" accuracy is needed on something like this, myself I'd be more than happy with 0.001" and a bit of play in the dowels so that the vice jaws can take up any slight variations in the workpiece. In that case after hardening a sheet of glass and some abrasive papers should allow you to hand finish the jaws.

Rather than through hardening consider a surface treatment like nitriding. A 12 hour nitride will give you about 0,004" depth of glassy hard surface up around60 plus Rockwell with little distortion. Where are you based ?

With 1018 being a low carbon steel its likely to have to be a surface hardening as there is not enough in teh metal to do anything else with it. Its only like EN3B

Charles,

This won't really help with the dimensional aspects, but it describes the process of 'Black Polishing'.

**LINK**

... Adapt as appropriate.

MichaelG.

Maybe sacrilege; but worth a thought:

Consider the possibility of using a pair of Slips ['Jo Blocks'], or thin Parallels, as jaw facings.

MichaelG

I read this as Charles wanting to practice precision work, rather than needing a super accurate vice, so getting someone else to surface grind or using pre-made parts won't help.

The real question is how to I make accurate parts with a hard, well finished surface.

My suggestion would be make (very) slightly over-size from case hardenable steel, case harden, then jury rig up a temporary 'surface grinder', and finish that way.

Very hard to get a finish that is both 'mirror' and accurate (which is why gauge blocks cost so much).

Neil

.

Joseph Whitworth explained the way to achieve accuracy of 'flat' surfaces.

You either have a master reference surface [an Optical Flat is good] available [which may, in this context be considered as 'cheating'], or you need to make three surfaces that all match to your required standard.

Essential reading is linked here

MichaelG.

Edited By Michael Gilligan on 08/03/2016 10:00:58

The flat part is not so hard to get its the opposite face being parallel and the two sides square to those and all ending up at the required dimension.

,

Whitworth was pretty clued-up on that too, Jason

MichaelG.

I suspect the OP is thinking of using the vice precision to allow accurate filing - noticing the file skidding across hardened surfaces. If that's the idea I would be inclined for forget it. When people are filing they don't file the vice as well. A pair of rollers that could be mounted on a lathe to allow work to filed true used to be popular. Ideally the rollers would need to be hardened as well. Maybe something like that could be done.

Things can be filed flat against a reference because files especially larger ones should have a bit of a curve in them. When used heavily this flattens out, lightly it doesn't. Also rifflers and stones can be used to refine the surface.

The nearest type of vice in terms of precision he could buy would be a tool makers vice. The idea of these is that work could be held in them and moved from machine to machine or even into a bench vice for different operations. If made correctly they are very precise. Some are hardened and ground all over as they might even be mounted on there side. One problem is £££££££££££££ new but good used ones do turn up.

Nitriding does sound great but there can still be distortion. A mad training exercise - makes some huge milling cutter chucks and nitride them to save grinding. They finished up being ground. Moulding tools too. In practice when things are hardened achieving the sort of accuracy the op is after can be tricky. I've surface ground the table of a surface grinder several times to do that. They only need a thou or so taking off but when the 1/10's count it helps. In fact it can result in close to 0 tenths 'cause you do the job immediately after grinding the table having let things warm up for 10min or so first.

The easiest way of obtaining flat polished surfaces is to lap them. The lap is usually cast iron with a castelated surface leaving lots of squares circa 1/4 - 1/2 across that have been ground flat. 3M make some lapping films which mounted on a surface plate or something pretty flat could be a lot easier to use.

A drill press plus using the end of a bar as a lap can produce the same sort of accuracy as scraping if the table is dead flat. It's usually just used for a decorative finish.

There are 2 simple machines that are rather well known to be able to produce flat surfaces that need little work. One the shaper needs to be pretty good nick. The other is a linisher. Those needs to be well made and set up. A horizontal mill can too.

Either way case hardening may be a better option. Very slow heating but variations in section are still likely to cause distortion.

John

-

Thanks for the replies! Some of you have hit it on the head. I want to try some precision machining. I currently am making some work aids, fixtures and jigs for a music chair manufacturer. The tolerances range from a few thousands to just slop! I had to file a screw head and griped it with a pair of vise grips with aluminum sheets to protect the threads. I filed it a little crooked so I want to make a small pair of blocks to put the screw in and file it straight. Call it a work holder instead of hand vise. I have made some in the past and eventually you get a wear area where the file touches.

I am retiring in the next year and am setting up my own little shop. This is just a learning project to see how tight and perfect I can make some things. It all needs to be done in my shop, so I don't want to send it out for treatment. My heat treating in the past has been to heat a chisel to cherry and quench and anneal. I have two kilns sitting here so I thought I would try a more controlled procedure.

I'm using 1018 because I have it along with 6061 aluminum and mild structural steel (A36?). Will work for steel or tools! Even Cash! I will be happy to try your recommendations for better steel if I can come close to lapping and finishing square and parallel. Same for heat treating vs case hardening. I down loaded the Whitworth book and am looking into black polishing. Trying to figure out how to hold the item on the lap above to keep parallel.

I live in North Carolina, USA. Been doing heavy duty machine and truck repairs for over 40 years. That includes inventing what ever is needed building engines and transmissions and welding. Also milling and lathe work as the machinists let me close to their machines when they are too busy.

I appreciate the answers and look forward to trying them out. Thanks again for all the help and look forward to more ideas!!

[Quote]

Essential reading is linked here

MichaelG.

[/Quote]

Yes, a great book, Michael.

Another, somewhat more recent, great read is Foundations of Mechanical Accuracy by Wayne R Moore.

I don't have a link to hand, but it's available on the web.

Roger

A 10" millsaw file, six-inch steel ruler, engineer's try square and a bit of patience will get you within your .0005". Then you could case harden it using Kasenit or other case-hardending compound.

To get down to .0002" tolerances that you are aiming for on hardened surfaces, usual processes would be surface grinding, or by hand using abrasive rubbing stones.

Have a look at the youtube videos by Dan Gelbart titled "Making prototypes". They won't tell you everything but there are some interesting bits.

Regards.

David.